The invention relates to a forming tool for pipe ends with a fixing device holding the pipe and a flanging die acting on the projection of the pipe end, wherein the flanging die has a mandrel driven into the pipe end and a forming die surrounding the mandrel and the mandrel and the forming die are held in a housing.
Forming tools of this type are required to upset or pressure-form pipe ends, i.e., to shape the pipe end. Examples of pipes are primarily hydraulic or pneumatic pipes made of metal, in particular steel or aluminium which are used to carry fluids, in particular, in motor vehicles. These pipes have to be connected in a fluid-tight manner, for which purpose their ends have to be prepared accordingly. The pipe ends are provided with a peripheral bead by plastic shaping, the end face beaded lip directed radially inwardly being formed by the pipe end.
A tool is used for forming as shown, for example, in FIGS. 4 and 5. After the pipe 152 has been fixed in a fixing device 154 in such a manner that the pipe end projects beyond the fixing device 154 by a predetermined amount, this pipe end is plastically formed axially by means of a flanging die 112. In the process, a mandrel 148 is first introduced into the pipe end 150 and subsequently the region of the pipe end 150 located downstream of the end supported by the mandrel 148 is widened by means of a forming die 140. The flanging die 112 is fed axially in the direction of the pipe end 150 until its housing 110 contacts the fixing device 154 or a corresponding stop.
It has been found that owing to the fixing tolerances of the pipe 152, i.e., owing to different projecting amounts of the pipe end 150, a significant number of unusable forming operations are carried out. There is in fact the risk with an excessive projection of a portion of the pipe material being squashed between the housing 110 and the fixing device 154, as shown in FIG. 6. This expelled collar or flash 158 prevents a cap nut from being applied to the pipe end 150.
The object of the invention is therefore to provide a forming tool for pipe ends with which the pipe end can be produced more precisely even if the pipe projection beyond the fixing device has different values.
This object is achieved according to the invention with a forming tool of the type mentioned above in that a flanging die limiting the forming die is provided.
The limiting die provided in the forming tool according to the invention provides the fundamental advantage that the end of the pipe projecting beyond the fixing device is completely enclosed prior to forming so this end can be widened to the maximum during forming until it contacts the limiting die. Consequently the formation of a collar or flash which would prevent slipping-on of the cap nut is avoided.
The limiting die advantageously forms the leading end face of the forming tool facing the pipe end. During the forming process, the free pipe end is therefore completely surrounded by the limiting die and the limiting die contacts the fixing device and thus closes the forming space. In the process the limiting die projects beyond the housing axially in the direction of the pipe end.
In one embodiment, the limiting die is resiliently mounted in the axial direction via a spring. This means that during forming the limiting die is driven into the housing so it does not represent an obstacle to the housing approaching the fixing device. The limiting die is guided in an axial aperture of the housing here. The limiting die is advantageously sleeve-shaped.
In a further embodiment, the fixing device has a receptacle for the limiting die which driven into the fixing device at least during forming, so it does not hinder the axial advance of the housing in the direction of the fixing device.
The limiting die is a sleeve-shaped with, in particular, a circular internal cross-section. This internal cross-section limits the external cross-section or forms this external cross-section of the end bead. A shape different from a circle can also be impressed on this end bead.
In one development, the limiting die forms an axial bearing for the forming die so the forming die is guided axially displaceably in the limiting die. The limiting die in its turn is guided in an axial aperture of the housing. Consequently the pipe material is prevented from being driven between the limiting die and the forming die during forming.
In a preferred variation, the forming die is mounted axially displaceably on the mandrel. A separate axial bearing for the radially inner support of the forming die is dispensed with owing to this measure. Simple central lubrication for the forming die and the limiting die is also possible.
To limit the forming force, the forming die can be driven axially into the housing counter to the force of a spring. Both the spring for the forming die and the spring for the limiting die can be designed as mechanical, magnetic, hydraulic or pneumatic springs. The springs are supported here on the housing and, in particular, can be adjusted.
Simple assembly of the flanging die according to the invention is achieved in that the housing has a three-stage aperture and all components can be inserted into the housing from the end remote from the pipe end. Maintenance and repair work is also facilitated hereby. In addition, additional bearing elements are dispensed with as the individual components are nested and mutually supported.
Relatively simple access to the individual components is achieved in that the end of the housing remote from the pipe end has a screw cap. If one and/or the other spring is supported on the screw cap, the spring force can also be adjusted thereby. This can of course also be changed by changing the fluid pressure or by exchanging the springs used.